Restrictive convenant

[Cosmois]

We are trying to buy a house that we plan to extend. We have just found this restrictive convenant on the house:

That any messuage or other building erected on the said land thereby conveyed should be in all respects in conformity with plans and elevations to be first approved in writing by the Vendor and with the amenities of the adjoining property and nothing should be done or permitted to be done on the said land which might be or become a nuisance or annoyance to the Vendor or to the adjoining owners or the neighbourhood.

This was back in the 30s, I presume the original vendor is now dead. What does this mean in practice? We are planning to extend the house, should we just give up and find somewhere else?

If the vendor is dead then there will be no one to impose the covenant and it is pretty much not worth the paper it is written on. They rarely get enforced anyway in my experience but other people may well have different experiences.

The "vendor" will usually be the original plot of land from which the house plot was carved out of. This was to stop the new neighbour causing the original owners land to be devalued by intrusive development. So at least one of the neighbour houses is likely to have retained power of veto on your plans.
Investigate on the basis that the veto is still active and that you need the other homeowner to agree to the reno prior to the purchase.
Plus on the basis that you bought with the restriction that the court would grant an injunction against you after your sale. Ask the seller what houses are involved and if you really like the house ask the seller to get the covenant amended/withdrawn.